A variety of security systems are available today to protect homes, businesses and other locations. The technologies used by these systems include infrared and ultrasonic motion detectors, video surveillance systems, or thermal systems. Some systems are wired to monitoring services or patrolled by guards for around-the-clock protection. These systems typically cost thousands of dollars to install and can be much more expensive. Some systems use sophisticated image processing algorithms to identify human shapes or faces in an image taken from a protected scene.
General methods for identifying people are known in the art, for example, methods based on image processing algorithms. US Patent Application 2006/0062429 suggests a method for detecting motion in the image and comparing two images take at different subsequent times. Applying an image processing algorithm determines if at least one shape represents a person. US Patent Application 2006/0200841 suggests a method of identifying people in an image by identifying human-like shapes in a captured image. These types of methods image processing are expensive to implement and require substantial processing power.
Eye tracking applications are also known, in particular for use with handicapped people. These applications, which also use expensive signal processing hardware and software, typically require the person to sit in a distance of up to 60 centimeters of the screen, and are only suited for tracking the eyes of a single person.
Photographs of people taken with a camera using flash often exhibit a phenomenon called red-eye. The effect is caused by reflection of the camera flash from the back of the eye. Typically the pupil of the eye develops a greater or lesser degree of red color. However, other colors can occur (such as gold-eye) and the effect may be sufficiently intense to eliminate all detail in the eye so that the pupil and iris cannot be distinguished, forming a single red blob. The likelihood of red-eye is increased when the eye is dark-adapted and the pupil is wide open, which represents precisely the low light situation that requires flash illumination. In such a case, the pupil does not have time to close before a reflection occurs from the back of the eye. The effect is further increased for inexpensive or compact cameras having a flash mounted close to the axis of the lens, which increases the likelihood that reflected light will enter the lens. This has the unfortunate effect that the most pronounced red-eye can occur when the eye is small compared to the size of the image, and so is hardest to correct. Further impediments to correction result, for instance, from reflections caused by contact lenses.